Efforts have been made to determine the etiological agent involved in Multiple Sclerosis. Several new techniques including direct migration inhibition, lymphocyte cytotoxicity and complement mediated antibody cytotoxicity have been utilized. Cellular immune responses of MS patients and matched controls against measles, Rubella, herpes I and II, and CMV were similar. Humoral immune studies confirmed higher measles antibody titers in MS patients than controls. However, other humoral immune tests against rubella, herpes I and II, and CMV indicate that the humoral immune responses of MS patients is not different from that of controls. We failed to confirm the presence of a mouse circulating polymorphonuclear neutrophil depression factor in brain suspensions of MS patients. Efforts to develop a new test for CMV has been successful. We have developed the ELISA technique to measure CMV antibody, the use of one dilution of serum in the ELISA technique may make possible rapid determination of antibody levels against CMV. BIBLIOGRAPHIC REFERENCES: Castellano, G.A., Hazzard, G.T., Madden, D.L. and Sever, J.L.: ELISA for Determination of Antibody to Cytomegalovirus Comparison to the Indirect Hemagglutination Test. J. of Infect. Dis. October, 1977. (In Press); Hall, W.T., Madden, D.L., Mundon, F.K., Brandt, D.E. and Clarke, N.P.: Protective Effect of Immune Serum Globulin (ISG) against Hepatitis a Infection in a National Epidemic. Amer. J. of Epid. August, 1977. (In Press).